In numerous optical reader systems and robot vision systems, images are binary digitized prior to being processed in order to make such processing possible, and in particular, in character recognition systems the images are binary digitized prior to embarking on the recognition phase, per se.
The images are thus sampled using a grid which is generally rectangular, and each pixel which corresponds to a single grid point is binary digitized using a single bit whose value depends on whether the pixel belongs to the pattern or to the background of the image. For example, when the image is constituted by a black pattern on a white background, a one value bit may correspond to black and zero value bit may correspond to white.
When processing images, and in particular when performing character recognition, it is necessary to accurately locate special points such as nodes and the ends of lines which constitute a pattern within the image.
The large number of pixels which constitute a pattern results in a direct search for special points giving rise to a very great deal of calculation, and to results which are often inaccurate.
In order to simplify the problem of detecting special points as much as possible, and also to simplify the problem of following a pattern as such as possible, algorithms are being sought for skeletonization of binary images.
Performing such algorithms in software generally gives rise to calculation times which are incompatible with most practical applications, and in particular which are incompatible with applications operating in real time, e.g. systems for recognizing characters in mail sorting.
The present invention thus seeks to provide apparatus for processing images which have been sampled using a rectangular grid and which are digitized at one bit per pixel, said apparatus being intended to mitigate the above-specified drawbacks.